WO2015146775A1

WO2015146775A1 - Electric brake device

Info

Publication number: WO2015146775A1
Application number: PCT/JP2015/058220
Authority: WO
Inventors: 唯増田
Original assignee: Ntn株式会社; 唯増田
Priority date: 2014-03-27
Filing date: 2015-03-19
Publication date: 2015-10-01
Also published as: US10100891B2; US20170009830A1; CN106132795B; EP3124345A1; EP3124345A4; EP3124345B1; JP6309322B2; CN106132795A; JP2015186972A

Abstract

Provided is an electric brake device that can improve control precision without requiring a cost increase. This electric brake device comprises an electric motor (2), a brake rotor (5), a friction pad (6), a transmission mechanism (4), a brake force command means (26a), a brake force estimating means (30), a motor rotation angle detecting means (28), and a control device (7). The motor rotation angle detecting means (28) is used in a brake force region that is between the exertion of minimum brake force and maximum brake force, and has a resolution that is higher than the resolution of a motor rotation angle that generates a brake force variation that is equivalent to the minimum brake force resolution of the brake force estimating means (30). The control device (7) has a resolution interpolating means (37) that uses the motor rotation angle detected by the motor rotation angle detecting means (28) to interpolate the minimum resolution of the brake force that is found by the brake force estimating means (30).

Description

Electric brake device

Related applications

This application claims the priority of Japanese Patent Application No. 2014-65267 filed on Mar. 27, 2014, the entire contents of which are incorporated herein by reference.

This invention relates to an electric brake device capable of improving control accuracy without requiring an increase in cost.

Conventionally, the following are proposed as an electric brake device.
(1) By depressing the brake pedal, the rotational motion of the motor is converted into a linear motion through a linear motion mechanism, and the brake pad is pressed against the brake disc to apply a braking force (Patent Document 1).
(2) An electric linear actuator using a planetary roller screw mechanism (Patent Document 2).
(3) Brake force estimation means using a strain sensor (Patent Document 3).

JP-A-6-327190 JP 2006-194356 A JP 2003-287063 A

In the electric brake device of the above (1) that converts the rotational motion of the motor into a linear motion, and the electric brake device of the above (2) that uses a planetary roller screw mechanism, a brake force estimating means is provided for accurately controlling the brake force. It is necessary to provide a control system having a feedback element. At that time, it is common to configure a digital control system that repeats the calculation every predetermined sampling time using an arithmetic unit such as a microcomputer.

At this time, the shorter the sampling time is set, the higher the speed and accuracy of the control becomes possible, while the higher the requirement for the resolution of the brake force estimating means. If the resolution is insufficient, the responsiveness of the control system is impaired, and the control accuracy may be reduced. For example, in the ABS control, it is required to control the braking force at high speed and with high accuracy in order to prevent the wheel from slipping. Insufficient response speed and control accuracy may cause problems such as the wheels exceeding the slip limit and adversely affecting steering, or conversely, the braking distance may increase due to a decrease in braking force.

In the electric brake device (3) that detects deformation and distortion due to reaction force when the friction pad is pressed and estimates the braking force, it is necessary to greatly deform the constituent members in order to use a highly accurate sensor. Therefore, a decrease in rigidity and durability may be a problem. In addition, since shielding and insulation that are highly effective as noise countermeasures may be required, there is a possibility of increasing costs and mounting space.

An object of the present invention is to provide an electric brake device capable of improving control accuracy without requiring an increase in cost.

Hereinafter, in order to facilitate understanding, the present invention will be described with reference to the reference numerals of the embodiments for convenience.

The electric brake device according to a first aspect of the present invention includes an electric motor 2, a brake rotor 5, a friction pad 6 that comes into contact with the brake rotor 5 to generate a braking force, and a rotational motion of the electric motor 2. The transmission mechanism 4 that converts the motion of the friction pad 6, the brake force command means 26 a that generates a target brake force command value from the operation amount of the brake operation means 29, and the friction pad 6 is pressed against the brake rotor 5. Brake force estimating means 30 for obtaining an estimated value of the brake force, motor rotation angle detecting means 28 for detecting the rotation angle of the electric motor 2, and controlling the electric motor 2 according to the command value and the estimated value of the brake force An electric brake device provided with a control device 7,
The motor rotation angle detection means 28 has a resolution higher than a motor rotation angle that generates a brake force fluctuation equivalent to the minimum brake force resolution of the brake force estimation means 30;
The control device 7 has resolution interpolation means 37 for interpolating the minimum braking force resolution obtained by the braking force estimation means 30 with the motor rotation angle detected by the motor rotation angle detection means 28.
The minimum brake force is a minimum brake force that can be detected by the brake force estimating means 30. The maximum brake force is a brake force that is the maximum value of the command value generated by the brake force command means 26a. The “resolution” represents a minimum interval between a detectable braking force or a motor rotation angle, and is represented by a bit number or the like in digital data. For example, the resolution is the value obtained by dividing the maximum value M of the braking force (or motor rotation angle), which is a continuous amount, by the number obtained by adding 1 to the L bit (L is a natural number) digital maximum value (2 ^L −1) That is, the value per bit (= M / 2 ^L ) with respect to the maximum value M of the braking force (or motor rotation angle).

According to this configuration, the motor rotation angle detection means 28 has a higher resolution than the motor rotation angle that generates a brake force fluctuation equivalent to the minimum brake force resolution of the brake force estimation means 30. Since the motor rotation angle detection means 28 is inexpensive and has high resolution, it is easy to mount the motor rotation angle detection means 28 in the electric brake device. Further, since the motor rotation angle detection means 28 can be an existing detection means originally provided in the electric motor 2, it is not necessary to secure a mounting space for the motor rotation angle detection means, and a dedicated sensor is used as the electric brake. Since there is no need to add a new device, the cost can be reduced.

During the transition of the braking force from zero to the maximum value, for example, the detected motor rotation angle changes the full scale from the angle “0” to the maximum angle in the motor rotation angle detection means 28 a plurality of times. How much the motor rotation angle detected by the motor rotation angle detection means 28 changes with respect to the minimum resolution of the braking force can be estimated from information given in advance such as caliper rigidity and equivalent lead. Based on this estimation result, the resolution interpolation means 37 of the control device 7 interpolates the minimum resolution of the braking force obtained by the braking force estimation means 30 by the motor rotation angle detected by the motor rotation angle detection means 28. Then, for example, even when the resolution for detecting the braking force is lower than the required resolution for the target braking force, the intermediate value can be interpolated and controlled by the motor rotation angle. Thus, the control accuracy can be improved without requiring an increase in cost.

The brake force estimation means 30 may use a detection value of a load sensor 13 that detects an axial load of the transmission mechanism 4. In this case, the control device 7 advances the linear motion portion 14 of the transmission mechanism 4 from the position away from the brake rotor 5 to the outboard side so that the friction pad 6 contacts the brake rotor 5, and the reaction force is applied to the load sensor. The minimum detection value that can be detected at 13, that is, the braking force is acquired. The brake force detected by the load sensor 13 gradually increases in accordance with the operation amount that further depresses the brake operation means 29. By using this load sensor 13, it is possible to detect the braking force with higher accuracy than obtaining the estimated value of the braking force from the sensor output of the brake operating means 29 and the motor current.

The resolution interpolation unit 37 includes:
Determining the relationship between the braking force estimation result when the braking force calculated by the braking force estimation means 30 changes by a predetermined value or more and the motor rotation angle detected by the motor rotation angle detection means 28;
Interpolating intermediate values up to each subsequent braking force estimation result obtained by adding positive and negative addition values determined in the braking force estimation result based on the motor rotation angle detected by the motor rotation angle detection means 28 It is also good.
The predetermined value is arbitrarily determined according to a request from results of experiments and simulations, for example.

The resolution interpolation unit 37 may increase the determined value as the difference between the brake force command value generated by the brake force command unit 26a and the brake force estimation result increases. The resolution interpolation unit 37 increases the predetermined value as the change rate of the difference between the brake force command value generated by the brake force command unit 26a and the brake force estimation result increases. May be.

When the predetermined value is increased, the resolution is reduced but the noise resistance is improved. When the difference between the braking force command value and the braking force estimation result or the change rate of the difference is large, the resolution interpolation means 37 has a relatively small effect of interpolating the resolution. A so-called thinning process for increasing the predetermined value according to the rate is executed. Thereby, the calculation load of the control device 7 can be reduced.

The control device 7 has a calculation means 37 for associating a motor rotation angle detected by the motor rotation angle detection means 28 with a predetermined motor rotation angle and a braking force based on a braking force obtained by the braking force estimation means 30. You may have. For example, the calculation means 37 determines the absolute motor rotation angle by specifying the number of rotations of the motor rotation angle in the plurality of rotations based on the braking force.

While the braking force changes from zero to the maximum value, the motor rotation angle detected by the motor rotation angle detection means 28 changes the full scale from the angle “0” to the maximum angle several times, and also due to friction pad wear, etc. Since the piston position at which the friction pad and the brake rotor start to contact, that is, the motor rotation angle changes, the absolute angle of the motor rotation angle for accurately exhibiting the desired braking force is unknown only by the motor rotation angle detection means 28. . According to this configuration, the calculation means 37 of the control device 7 exhibits a desired braking force from the relationship between the motor rotation angle detected by the motor rotation angle detection means 28 and the braking force obtained by the brake force estimation means 30. The absolute angle of the motor rotation angle to be obtained can be obtained. Therefore, it is possible to improve the control accuracy without requiring an increase in cost.

Any combination of at least two configurations disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the invention.

The present invention will be understood more clearly from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same reference numerals in a plurality of drawings indicate the same or corresponding parts.

It is sectional drawing of the principal part of the electric brake device which concerns on one Embodiment of this invention. It is a block diagram of a control system of the electric brake device. It is a conceptual diagram explaining the brake operation | movement in the electric brake device. 4 is a flowchart showing an example of interpolating a brake force estimated value with a motor rotation angle in the electric brake device.

An electric brake device according to one embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the electric brake device includes a housing 1, an electric motor 2, a speed reduction mechanism 3 that decelerates rotation of the electric motor 2, a linear motion mechanism 4 that is a transmission mechanism, a brake rotor 5, and the like. And a friction pad 6, a lock mechanism (not shown), and a control device 7 for controlling the electric motor 2. An electric motor 2 is supported on a housing 1 that is a caliper. A linear motion mechanism 4 that loads a braking force to the brake rotor 5 (in this example, a disk rotor) by the output of the electric motor 2 is incorporated in the housing 1. The open end of the housing 1 is covered with a cover 8.

The linear motion mechanism 4 will be described. The linear motion mechanism 4 is a mechanism for converting the rotational motion output from the speed reduction mechanism 3 into a linear motion and bringing the friction pad 6 into contact with and separating from the brake rotor 5. The linear motion mechanism 4 includes a rotary shaft 9 that is rotationally driven by the electric motor 2, a conversion mechanism unit 10 that converts the rotary motion of the rotary shaft 9 into linear motion,

restraint portions

11 and 12, a load meter and a force. And a load sensor 13 also called a sensor. The conversion mechanism section 10 includes a linear motion section 14, a bearing member 15, an annular thrust plate 16, a thrust bearing 17, a plurality of rolling bearings 18, a carrier 19, sliding

bearings

20 and 21, and a plurality of planetary planets. And a roller 22.

A cylindrical linear motion portion 14 is supported on the inner peripheral surface of the housing 1 so as to be prevented from rotating and movable in the axial direction. On the inner peripheral surface of the linear motion portion 14, a spiral protrusion is provided that protrudes a predetermined distance radially inward and is formed in a spiral shape. A plurality of planetary rollers 22 are engaged with the spiral protrusions.

A bearing member 15 is provided on one axial end side of the linear motion portion 14 in the housing 1. The bearing member 15 has a flange portion extending radially outward and a boss portion. A plurality of rolling bearings 18 are fitted in the boss portions, and the rotary shaft 9 is fitted to the inner ring inner surface of the rolling bearings 18. The rotating shaft 9 is rotatably supported by the bearing member 15 via a plurality of rolling bearings 18.

A carrier 19 that can rotate about the rotation shaft 9 is provided on the inner periphery of the linear motion portion 14. The carrier 19 has disks that are arranged to face each other in the axial direction. The disk close to the bearing member 15 may be referred to as an inner disk, and the other disk may be referred to as an outer disk. Of the outer side disk, a side surface facing the inner side disk is provided with a spacing adjusting member that protrudes in the axial direction from the outer peripheral edge portion on the side surface. In order to adjust the interval between the plurality of planetary rollers 22, a plurality of the interval adjusting members are arranged at equal intervals in the circumferential direction. Both the disks are integrally provided by these distance adjusting members.

The inner disk is rotatably supported by a sliding bearing 20 fitted between the rotating shaft 9 and the inner disk. A shaft insertion hole is formed in the center of the outer disk, and a slide bearing 21 is fitted in this shaft insertion hole. The outer disk is rotatably supported on the rotary shaft 9 by the slide bearing 21. At both ends of the rotating shaft 9, constraining

portions

11 and 12 that receive a thrust load and constrain the axial position of the rotating shaft 9 are provided. Each restraining

part

11 and 12 contains the stopper piece which consists of a washer etc., for example. Retaining rings for preventing the restraining

portions

11 and 12 from coming off are provided at both ends of the rotating shaft 9.

The carrier 19 is provided with a plurality of roller shafts 23 at intervals in the circumferential direction. Both end portions of each roller shaft 23 are supported across the inner side disk and the outer side disk. That is, a plurality of shaft insertion holes each having a long hole are formed in both discs, and both end portions of each roller shaft 23 are inserted into the respective shaft insertion holes, and the roller shafts 23 are radially formed within the range of the respective shaft insertion holes. It is supported movably. Elastic rings 24 that urge the roller shafts 23 inward in the radial direction are respectively hung on both ends in the axial direction of the plurality of roller shafts 23.

Each planetary roller 22 is rotatably supported by each roller shaft 23, and each planetary roller 22 is interposed between the outer peripheral surface of the rotary shaft 9 and the inner peripheral surface of the linear motion portion 14. Each planetary roller 22 is pressed against the outer peripheral surface of the rotating shaft 9 by the urging force of the elastic ring 24 spanned across the plurality of roller shafts 23. As the rotating shaft 9 rotates, each planetary roller 22 that contacts the outer peripheral surface of the rotating shaft 9 rotates due to contact friction. On the outer peripheral surface of the planetary roller 22, a spiral groove that meshes with the spiral protrusion of the linear motion portion 14 is formed.

The speed reduction mechanism 3 is a mechanism that transmits the rotation of the electric motor 2 at a reduced speed to the output gear 25 fixed to the rotary shaft 9, and includes a plurality of gear trains (not shown). In this example, the speed reduction mechanism 3 can sequentially transmit the rotation of an input gear (not shown) attached to a rotor shaft (not shown) of the electric motor 2 to the output gear 25 by the gear train. The locking mechanism is configured to be switchable between a locked state in which the braking force slack operation of the linear motion mechanism 4 is prevented and an unlocked state in which the braking force slack operation is allowed.

FIG. 2 is a block diagram of the control system of this electric brake device. The control device 7 of the electric brake device is an inverter device 27, and an electric control unit for controlling the vehicle as a whole is applied as the ECU 26 which is a host control means of the inverter device 27, for example. The ECU 26 is provided with a brake force command means 26a. The brake force command means 26a is configured to use a predetermined conversion function of a LUT (Look / Up / Table) or a library (Library) in accordance with the output of the sensor 29a that changes according to the amount of operation of the brake pedal as the brake operation means 29. Used to generate and output a target brake force command value. The brake operation means 29 is not limited to a pedal input type as long as it is a means for an operator to instruct braking, and may be a button input type, a lever input type, or the like.

The inverter device 27 includes a brake force estimating means 30 for obtaining an estimated value of a brake force that presses the friction pad 6 (FIG. 1) against the brake rotor 5 (FIG. 1), and a power circuit unit 31 provided for each electric motor 2. And a motor control unit 32 for controlling the power circuit unit 31 and a current detection means 34.

The brake force estimation means 30 calculates an estimated value of the corresponding brake force from the output of the sensor 29a that changes according to the operation amount of the brake operation means 29 and the motor current detected by the current detection means 34, in the LUT or the library. It is obtained by calculation using a predetermined conversion function or the like. The relationship between the output of the sensor 29a, the motor current, and the estimated value of the braking force is determined in advance by results of experiments and simulations, and is recorded in the recording means 38 so as to be rewritable.

In addition to this, the brake force estimating means 30 may use the detection value of the load sensor 13 that detects the axial load of the linear motion mechanism 4. In this case, when the driver of the vehicle depresses the brake operating means 29 from the released state, the control device 7 outboards the position where the linear motion portion 14 (FIG. 1) is separated from the brake rotor 5 (FIG. 1). The friction pad 6 comes into contact with the brake rotor 5 by being advanced to the side (FIG. 1). By detecting the reaction force at the time of this contact by the load sensor 13, the minimum detectable value, that is, the minimum braking force is obtained.

The brake force detected by the load sensor 13 gradually increases in accordance with the operation amount that further depresses the brake operation means 29. By using the detection value of the load sensor 13, it is possible to detect the braking force with higher accuracy than obtaining the estimated value of the braking force from the output of the sensor 29a and the motor current.

The motor control unit 32 includes a computer having a processor, a ROM (Read Only Memory) having a program executed by the processor, and an electronic circuit such as a RAM (Random Access Memory) and a coprocessor (Co-Processor). Composed. The motor control unit 32 converts the braking force command value given from the braking force command means 26a and the estimated braking force value estimated by the braking force estimation means 30 into a current command expressed by a voltage value. The current command is given to the power circuit unit 31. The motor control unit 32 has a function of outputting information such as detection values and control values related to the electric motor 2 to the ECU 26.

The power circuit unit 31 includes an inverter 31b that converts the DC power of the power source 35 into three-phase AC power used to drive the electric motor 2, and a PWM control unit 31a that controls the inverter 31b. The electric motor 2 is composed of a three-phase synchronous motor or the like. The electric motor 2 is provided with motor rotation angle detection means 28 that detects the rotation angle of a rotor (not shown), for example, a rotation angle sensor or a rotary encoder. The inverter 31b is composed of a plurality of semiconductor switching elements (not shown), and the PWM control unit 31a performs pulse width modulation on the input current command and gives an on / off command to each of the semiconductor switching elements.

The motor control unit 32 has a motor drive control unit 36 as a basic control unit. This motor drive control unit 36 converts it into a current command represented by a voltage value in accordance with the command value and estimated value of the brake force described above, and sends a motor operation command comprising the current command to the PWM control unit 31a of the power circuit unit 31. Give value. The motor drive control unit 36 obtains a motor current flowing from the inverter 31b to the electric motor 2 from the current detection unit 34 and performs current feedback control with respect to the command value of the braking force. Further, the motor drive control unit 36 obtains the rotation angle of the rotor (not shown) of the electric motor 2, that is, the motor rotation angle from the motor rotation angle detecting means 28, so that efficient motor driving according to the motor rotation angle can be performed. In addition, a current command is given to the PWM control unit 31a.

The motor drive control unit 36 is provided with resolution interpolation means 37. The resolution interpolation unit 37 interpolates the minimum resolution of the braking force obtained by the braking force estimation unit 30 based on the motor rotation angle detected by the motor rotation angle detection unit 28. In this case, the motor rotation angle detection means 28 used in at least a part of the braking force region from the minimum braking force to the maximum braking force is applied to a brake equivalent to the minimum braking force resolution of the braking force estimation means 30. It has a higher resolution than the motor rotation angle that generates force fluctuations.

The resolution interpolating means 37 includes a braking force estimation result when the braking force obtained by the braking force estimating means 30 changes from a predetermined value by a predetermined value or more, and a motor rotation angle detected by the motor rotation angle detecting means 28. Determine the relationship. Further, the resolution interpolation means 37 adds each of the following braking force estimation results (estimation) obtained by adding positive and negative addition values (for example, positive when the brake pedal 29 is depressed and negative when the brake pedal 29 is released) determined in the braking force estimation result. The intermediate value existing up to (value) is interpolated based on the motor rotation angle detected by the motor rotation angle detection means 28 using the LUT, a predetermined conversion function of the library, or the like. As described above, the resolution interpolation unit 37 interpolates the minimum resolution based on the motor rotation angle.

Further, the calculation means 37 (FIG. 2), for example, converts the motor rotation angle θ (relative angle) detected by the motor rotation angle detection means 28 into a plurality of rotations (the brake force F obtained by the brake force estimation means 30). The absolute angle of the motor rotation angle is obtained by specifying the number of rotations of the motor rotation angle in the multiple times transition). While the braking force changes from zero to the maximum value, the motor rotation angle detected by the motor rotation angle detection means 28 changes a full scale from the angle “0” to the maximum angle (360 °: relative angle) a plurality of times. . Further, since the piston position (that is, the motor rotation angle) at which the friction pad and the brake rotor start to contact changes due to friction pad wear or the like, the motor for accurately exerting a desired braking force only by the motor rotation angle detection means 28. The absolute angle of rotation is unknown. According to the calculation means 37, the motor rotation angle for exerting a desired braking force from the relationship between the motor rotation angle detected by the motor rotation angle detection means 28 and the braking force obtained by the braking force estimation means 30 is calculated. The absolute angle can be obtained by using an LUT, an addition function of a library, an adder, or the like. Therefore, it is possible to improve the control accuracy without requiring an increase in cost.

The predetermined value is arbitrarily determined according to a request from the result of, for example, an experiment or a simulation, and is recorded in the recording means 38 so as to be rewritable. The resolution interpolation unit 37 has a change rate of a difference between the brake force command value generated by the brake force command unit 26a and the brake force estimation result or a difference between the brake force command value and the brake force estimation result. The larger the value, the larger the predetermined value.

When the predetermined value is increased, the resolution is reduced but the noise resistance is improved. If the difference between the braking force command value and the braking force estimation result, or the rate of change of this difference is large, the effect of interpolating the resolution is relatively small. In response to this, a so-called thinning process for increasing the predetermined value is executed. Thereby, the calculation load of the control device 7 can be reduced.

FIG. 3 is a conceptual diagram illustrating a brake operation in the electric brake device. Hereinafter, description will be made with reference to FIGS. 1 and 2 as appropriate. As shown in FIG. 3A, in this electric brake device, while the braking force changes from zero to the maximum value, for example, the detected motor rotation angle is a relative angle, and the motor rotation angle detecting means 28 The full scale from the angle “0” to the maximum angle (360 °) is changed a plurality of times.

FIG. 3B shows an example in which the braking force detection result is interpolated in a partial section surrounded by a one-dot chain line in FIG. How much the motor rotation angle detected by the motor rotation angle detection means 28 changes with respect to the minimum resolution of the braking force, that is, when the braking force changes by an amount corresponding to the minimum resolution, the motor rotation angle. It can be estimated from information given in advance such as caliper rigidity and equivalent lead. Based on this estimation result, the resolution interpolation means 37 of the control device 7 interpolates the minimum resolution of the braking force obtained by the braking force estimation means 30 by the motor rotation angle detected by the motor rotation angle detection means 28 as described above. To do. In this case, for example, even when the brake force detection resolution is lower than the target required brake force resolution, the intermediate value can be interpolated and controlled by the motor rotation angle.

FIG. 4 is a flowchart showing an example of interpolating the estimated brake force value by the motor rotation angle in this electric brake device. For example, this processing is started under the condition that the main power supply of a vehicle equipped with this electric brake device is turned on, and the resolution interpolation means 37, which is also referred to as computing means (FIG. 2), depresses the brake pedal 29 from the brake force estimating means 30. The brake force F (k) after being obtained is acquired, and the motor rotation angle θ (k) at the brake force F (k) is acquired from the motor rotation angle detection means 28 (step S1). The acquired braking force F (k) and motor rotation angle θ (k) are temporarily recorded in the recording means 38.

Next, the resolution interpolation unit 37 determines whether or not the acquired braking force F (k) has changed with respect to the latest past braking force F (k−1) recorded in the recording unit 38. (Step S2). When it is determined that the change has occurred (step S2: yes), the resolution interpolation unit 37 stores the braking force F (k) in the reference braking force Fb, and the motor rotation angle θ (k) at the braking force F (k). Is stored in the reference rotation angle θb (step S3). Thereafter, the resolution interpolation unit 37 stores F (k) in the current brake force F (step S4), and ends this process. The reference brake force Fb and the reference rotation angle θb are recorded in the recording means 38.

In step S2, it is determined that the brake force F (k) has not changed with respect to the latest brake force F (k-1) (step S2: no), and the resolution interpolation unit 37 determines that Nbit (N is a natural number). The motor rotation angle θ _LSB per brake force 1LSB corresponding to each of ^2N stages represented by the digital value is calculated (step S5). Specifically, θ _LSB = θ _M / ^2N with respect to the maximum value θ _M (absolute angle) of the motor rotation angle θ corresponding to the value (2 ^N −1) when all Nbits are 1. Next, the resolution interpolation unit 37 calculates the change rate θr of the motor rotation angle per brake force 1LSB (step S6). The change rate θr is obtained by dividing the value obtained by subtracting the reference rotation angle θb from the motor rotation angle θ (k) by the motor rotation angle _θLSB . Next, the resolution interpolation unit 37 calculates the current braking force F by the following equation F = Fb + (F _LSB × θr) (step S7). When F _LSB is expressed as a digital value of N bits (N is a natural number), the maximum value F _M of the brake force F corresponding to the value when all N bits are 1 (2 ^N −1), F _LSB = F _M / ^2N . Thereafter, this process is terminated. Note that LSB is a least significant bit (abbreviated as Least Significant Bit, LSB) is a bit position that means the smallest binary value in a computer.

Incidentally, since the electric brake device shown in FIG. 1 is mounted, for example, inside a wheel wheel of a vehicle on which the electric brake device is mounted, the volume of the electric brake device is preferably as small as possible. The pressing force of the friction pad 6 with respect to the motor torque of the electric brake device, that is, the braking force, is a performance that is the sum of the reduction ratio by the speed reduction mechanism 3 and the linear motion distance with respect to the rotational input of the linear motion mechanism 4, that is, equivalent to motor rotation. Determined by lead. The motor torque generally depends on the motor volume. That is, in order to reduce the volume of the electric brake device, it is necessary to make the equivalent lead sufficiently small.

On the other hand, when the friction pad 6 is pressed against the brake rotor 5, the peripheral members are deformed by this pressing force. It is necessary to project the linear motion mechanism 4 according to the amount of deformation. For example, in the case of a disc brake, generally, the deformation amount including the friction pad 6 and the housing 1, that is, the caliper at the time of exerting the maximum braking force is often about 0.5 mm to 1 mm. In the electric brake device according to this embodiment, for example, the equivalent lead per motor rotation is set to about 0.05 mm to 0.2 mm. With this setting, it is possible to realize a motor-sized electric brake device that can be mounted in a mounting space that is almost similar to an existing hydraulic brake.

According to the electric brake device described above, the motor rotation angle detection means used in the above-mentioned part of the brake force region is a motor rotation angle that generates a brake force fluctuation equivalent to the minimum brake force resolution of the brake force estimation means. Higher resolution. As this motor rotation angle detection means, an inexpensive and high resolution sensor, for example, a resolver, a GMR sensor, etc. are widely used in practical use. Therefore, it is easy to mount this motor rotation angle detection means in an electric brake device. It is. In addition, since the motor rotation angle detection means can be applied to the existing detection means inherent in the electric motor, it is not necessary to secure a mounting space for the motor rotation angle detection means, and a dedicated sensor is provided in the electric brake device. Costs can be reduced because there is no need to add new ones.

While the braking force transitions from zero to the maximum value, for example, the detected motor rotation angle is a full scale from the angle “0” to the maximum angle (360 °: relative angle) in the motor rotation angle detection means 28 a plurality of times. Transition to. How much the motor rotation angle detected by the motor rotation angle detecting means changes with respect to the minimum resolution of the braking force can be estimated by information given in advance such as caliper rigidity and equivalent lead. Based on this estimation result, the resolution interpolation means of the control device interpolates the minimum resolution of the brake force obtained by the brake force estimation means by the motor rotation angle detected by the motor rotation angle detection means. Then, for example, even when the resolution for detecting the braking force is lower than the required resolution for the target braking force, the intermediate value can be interpolated and controlled by the motor rotation angle. Thus, the control accuracy can be improved without requiring an increase in cost.

In this embodiment, an electric brake device of a disc brake type is applied as an example, but it is not limited to the disc brake type but may be a drum brake type. Further, although the planetary roller type has been described as the linear motion mechanism, other types such as a ball screw type and a ball ramp type may be used.

It should be noted that the present invention includes the following contents as an embodiment not premised on having the resolution interpolation means.
[Aspect]
An electric motor, a brake rotor, a friction pad that contacts the brake rotor and generates a braking force, a transmission mechanism that converts a rotational motion of the electric motor into a motion that the friction pad generates a braking force, and a brake operation A brake force command means for generating a target brake force command value from an operation amount of the means, a brake force estimation means for obtaining an estimated value of a brake force pressing the friction pad against the brake rotor, and a rotation angle of the electric motor An electric brake device comprising: a motor rotation angle detecting means for detecting the control signal; and a control device for controlling the electric motor in accordance with a command value and an estimated value of the brake force,
The motor rotation angle detection means has a resolution higher than the motor rotation angle that generates a brake force fluctuation equivalent to the minimum brake force resolution of the brake force estimation means;
The control device identifies the motor rotation angle in a plurality of rotations based on the brake force obtained by the brake force estimation unit, based on the motor rotation angle detected by the motor rotation angle detection unit. An electric brake device having a calculating means for obtaining an absolute angle of the motor rotation angle.

As described above, the preferred embodiments have been described with reference to the drawings. However, those skilled in the art will readily assume various changes and modifications within the obvious scope by looking at the present specification. Accordingly, such changes and modifications are to be construed as within the scope of the invention as defined by the appended claims.

2 ... Electric motor 4 ... Linear motion mechanism (transmission mechanism)
DESCRIPTION OF SYMBOLS 5 ... Brake rotor 6 ... Friction pad 7 ... Control apparatus 13 ... Load sensor 26a ... Brake force command means 28 ... Motor rotation angle detection means 29 ... Brake operation means 30 ... Brake force estimation means 37 ... Resolution interpolation means

Claims

From an operation amount of an electric motor, a brake rotor, a friction pad that comes into contact with the brake rotor to generate a braking force, a transmission mechanism that converts a rotational motion of the electric motor into a motion of the friction pad, and a brake operation means Brake force command means for generating a target brake force command value, brake force estimation means for obtaining an estimated value of the brake force that presses the friction pad against the brake rotor, and motor rotation for detecting the rotation angle of the electric motor An electric brake device comprising angle detection means and a control device that controls the electric motor in accordance with a command value and an estimated value of the brake force,
The motor rotation angle detection means has a resolution higher than the motor rotation angle that generates a brake force fluctuation equivalent to the minimum brake force resolution of the brake force estimation means;
The control device includes an electric brake device having a resolution interpolation unit that interpolates a minimum brake force resolution obtained by the brake force estimation unit based on a motor rotation angle detected by the motor rotation angle detection unit.
2. The electric brake device according to claim 1, wherein the brake force estimating means uses a detection value of a load sensor for detecting an axial load of the transmission mechanism.
In the electric brake device according to claim 1 or 2,
The resolution interpolation means includes
Determining the relationship between the braking force estimation result when the braking force calculated by the braking force estimation means changes by a predetermined value or more and the motor rotation angle detected by the motor rotation angle detection means;
Electric brake for interpolating intermediate values up to each subsequent brake force estimation result obtained by adding positive and negative addition values determined in the brake force estimation result based on the motor rotation angle detected by the motor rotation angle detection means apparatus.
4. The electric brake device according to claim 3, wherein the resolution interpolation means increases the difference between the brake force command value generated by the brake force command means and the brake force estimation result as the difference is larger. Electric brake device to increase the size.
4. The electric brake device according to claim 3, wherein the resolution interpolation means determines the larger the rate of change of the difference between the brake force command value generated by the brake force command means and the brake force estimation result, the larger the change rate. Electric brake device that increases the value obtained.
In the electric brake device according to claim 1,
The control device identifies the motor rotation angle in a plurality of rotations based on the brake force obtained by the brake force estimation unit, based on the motor rotation angle detected by the motor rotation angle detection unit. An electric brake device having a calculating means for obtaining an absolute angle of the motor rotation angle.